The present invention relates to a tubular element for passing flowable media, particularly chemically aggressive media.
Tubular elements for passing chemically aggressive media, such as pipes, valves and the like, have been proposed in the art. The known tubular elements are constituted by pressure resisting inexpensive metal, and generally are completely coated by a corrosion resisting cladding. Polytetrafluoroethylene is utilized for this cladding in many cases. It has been known to provide tubular body for such valves and to connect tubular sections with one another by means of flanges provided therein. In such a construction sleeves of synthetic plastic material which form the cladding have flanges which are axially pressed toward one another so as to form a sealed structure.
It has been also known to flange a cladding sleeve over a ball-shaped inner circumferential surface of a flange-shaped metal ring so as to form a valve seat for a valve member, which is constituted of a synthetic plastic material or is coated by the latter.
In a known check valve it is necessary to hold the valve member in the open position in which the valve member is lifted from the valve seat in a direction of passing of flowable media. A sufficient flow cross-section must be available through which the flowable medium can laterally pass the valve member when the latter is located in the open position. For this purpose, a ball-shaped spacer of polytetrafluoroethylene has been provided having fixing flanges at both its sides, between which flanges the spacer is supported by a splitted metallic ring. This spacer has a through opening which converges away from the valve seat up to a ball-shaped projection, and four additional axial openings are provided which are spaced from one another by an angular distance equal to 90.degree., and are arranged substantially outwardly of the central through opening so as to form a lateral flow cross section which is necessary in the open position of the valve member. The manufacture of such a spacer which is formed from a block of polytetrafluoroethylene, is complicated and expensive.